Flexible dowel



Dec. 12, 1939. 1 mg 2,183,484

FLEXIBLE DOWEL Filed May 18, 1937 j r/mr u? M92727 Patented Dec. 12, 1939 UNITED STATES eaTENT oFFicE 22 Claims.

This invention is directed to an improvement in expansion joints in concrete pavements and is concerned more particularly with a flexible dowel construction for use in such expansion joints to 5' provide the maximum strength at the joint, eliminate cantilever action on the ends of the slabs, permit complete freedom of expansion and contraction, with extreme simplicity in installation.

Expansion joints as conventionally provided f take care of the expansion and contraction of the adjacent concrete slabs under temperature changes, but in the continued use of the road-bed, the conventional expansion joint has proven ineffective to maintain a proper level of the meeting edges oi the adjacent slabs or to in effect provide any substantial strength at the joint proper.

The primary object of the present invention is the provision of a flexible dowel, duplicated in appropriate number, which forms a structural connection between the meeting edges of adjacent slabs and thereby provide that the load exerted on one slab adjacent the joint will be transferred to the other.

A further object is the provision of a flexible dowel in expansion joints which will maintain a unit connection between adjacent slabs, yield to completely free expansion and contraction of the slab, insure positive anchoring of the dowel in the respective slabs, and permit complete simplicity of. installation.

The invention is illustrated in the accompanying drawing, in which: 7

Figure 1 is a plan View, showing the flexible dowel in position. v

Figure 2 is a vertical sectional view, partly in elevation, of the flexible dowel in position.

Figure 3 is an elevation of one of the dowel plates.

Figure 4 is an edge view of the same.

Figure 5 is a diagrammatic View illustrating responsive movements of the dowel elements under contraction and expansion of the concrete slabs.

Expansion joints are employed in connection with the meeting ends of concrete slabs in constructing a road-bed and usually constitute a filler plates in duplicate, one of which is shown at 4. These plates are rectangular in plan and formed in the lower portion adjacent one side edge with an opening 5 and in a corresponding upper portion adjacent the other side edge with an opening 5 6. In line with each opening 5 and 6, the plate is formed with an elongated depression 1, with the depressions of. greatest depth at their ends adjacent the upper and lower edges of the plate,

as at 8, and of gradually decreased depth towards the opposite end where they merge into the surface of the plate.

Between each opening 5 and t and the end of the aligned depression, the plate is formed with a projection 9 which, as will later appear, serves to center the vertical portions of the bars used with the plate.

Each dowel unit includes two plates i and two bars ill for use with the plates. The bars are of identical construction, each including an intermediate vertical section ll, hereinafter termed the truss section, from the opposite ends of which extend in opposite directions upper and lower horizontal portions l2 and i3. From the end of one of the horizontal sections remote from the truss section there is extended a supporting section M which is substantially parallel to the truss section.

In providing for the use of the dowel, the filler section is formed at appropriate intervals with openings I5, to each of which the improved flexible dowel is applied. One of the plates 4 is applied to the filler section to overlie an opening l5, with the open sides of the depressions l and the projections 9 toward the opening; This results in having the projections 9 extend within the opening l5 while the closed sides of the depressions 7 extends beyond the vertical side of the filler section 3 towhich the plate is applied. One of the bars I0 is then passed through the upper opening of the connected plate so that the truss section of that bar rests within the opening and against the adjacent projection 9.

Assuming the bar installed, that indicated at the left of Figure 1, the truss section will extend 5 vertically of the opening in the filler section 3, the upper section l2 of the bar will extend at a right angles to the plate and to the filler section and the lower end of the supporting section Hi will rest on the bed surface it of the road-bed. In this installation, the lower section l3 of the bar will extend through the opening in the filler section 3 at right angles to the filler section and on a plane above the bed surface Hi. The other bar is then applied with its position reversed from that described. A second plate 4 is then applied to the opposite side of the filler section, with the openings 5 and 6 passed over the section M, section i 2 of the second bar and the section [3 of the first bar, the section l3 of the second bar passing through the opening 6 of the first applied plate. The plates are then secured at I! to the filler section 3 and the assembly is complete.

As assembled, the bars have their truss sections arranged side by side overlying and bearing upon the respective projections 9 of one plate and in line with the channels or depressions in the other plate. Each bar has a horizontal section above and slightly offset from a horizontal section of the other bar, and both bars are supported by their supporting sections l4.

Following the installation of as many flexible dowels as may be necessary depending upon the length of the joint and probably the contemplated load upon the road-bed, the filler section 3 is pinned in position in the usual manner and the concrete slabs l and 2 are poured. The horizontal sections l2 and I3 and the supporting sections I4 are completely embedded and rigidly held in the respectively adjacent concrete 7 slab.

Under expansion and contraction of the slabs,

the bends connecting the truss section of each bar ID with the horizontal sections I2 and I3 will obviously yield, so that the angle between the truss bar and horizontal sections, which is normally a right angle, becomes more acute on expansion movement of the concrete slabs and more obtuse on a contraction movement of the slabs. Under extreme expansion of the slabs, the opposite ends of the truss bars, may seat in the depressions I of opposed plates 4 to avoid interference, while the projections 9 serve to center the truss sections in line with the depressions.

Of course, any number of the dowel units may be employed and it is to be particularly noted that when in position the horizontal sections of the bars are rigidly anchored in the adjacent concrete slabs, that there is thus provided a positive structural connection between the slabs with the result that the load exerted on one slab is definitely and positively transferred to the other to maintain the effective plane of the slabs uniform at the joint. The loading stresses are transferred through the truss sections, and of particular importance is the fact that the expansion and contraction of the concrete slabs is substantially free of obstruction as the bends between the truss sections and the horizontal sections of each bar will yield to and compensate for any and all such movements of the concrete slabs.

Furthermore the plates 4 in completely closing the openings formed in the filler section 3 not only prevent any weakening of the section incident to the openings l5 but, as a matter of fact, strengthen such section as will be evident. If preferred, the filler sections may be formed with the openings and the initially applied plate 4 secured in position during the manufacture of the filler sections.

It is further to be noted that the dowel unit is of extreme simplicity in application, requiring no skill, particular knowledge, or adjustment, that when the filler section with the applied flexible dowels is pinned in place in the road-bed, the supporting feet 14 of the respective bars support the bars in proper relation to each other and to the filler section 3, so that the pouring of the concrete slabs may be proceeded with without the flexible dowel units requiring any attention.

What is claimed to be new is:

1. An expansion joint for concrete road work including a filler strip and duplicate unitary mechanical connections each extending continuously through the filler strip and having its 0pposite ends bonded in the adjacent slabs, said connections being constructed and arranged to take tension and compression to provide for load transference from one slab to the other while maintaining the mechanical connection during expansion and contraction of the slabs.

2. An expansion joint for concrete road work including a filler strip and a bar extending through the strip, said bar comprising parallel end portions bonded in concrete slabs and an intermediate truss section at an angle to and interconnecting said end portions, said truss section being substantially rigid to take tension and compression and extending between opposite faces of said filler strip.

3. A flexible dowel for expansion joints including plates to be secured to the opposite sides of a joint filler strip and in line with an opening in the strip, and a bar extending through the plates and terminally embedded in concrete blocks adjacent the strip, said bar having a truss section extending vertically of and between the plates.

4. A flexible dowel for expansion joints including plates to be secured to the opposite sides of a joint filler strip and in line with an opening in the strip, bars extending through the plates and terminally embedded in the concrete blocks adjacent the strip, each of the bars having an upper section on one side of the strip and a lower section on the opposite side of the strip relative to the surface of the slabs, each of the bars having a truss section movable between and relative to the plates in the expansion and contraction of the concrete slabs.

5. A construction as described in claim 4, wherein the upper and lower sections of the bars are reversely disposed on opposite sides of the filler strip.

6. An expansion joint for concrete slabs of a road-bed including a filler strip for the joint between the slabs, mechanical elements passing through the strip and terminally embedded in the concrete slabs beyond the strip, each element including a truss member constructed and arranged to take tension and compression disposed within the strip and extensions from the respective ends of the member, the respective extensions moving with the slabs relative to the truss member during contraction and expansion of the slabs.

7. A construction as defined in claim 6, wherein the extensions of the elements are in relatively offset horizontal planes beyond the filler strip.

8. A flexible joint-carrying dowel including plates to be secured to the filler strip, bars of approximately Z-form passing through the plates to provide extensions to be embedded in the slabs, the vertical element of the form being disposed between the plates, the respective bars being disposed with their upper and lower portions embedded in adjacent slabs in relatively reverse order.

9. A construction as defined in claim 8, wherein the plates are formed with depressions to permit movement of the vertical portions of the bars under extreme movement of the slabs.

10. A construction as defined in claim 8, wherein each of the bars is provided with a supporting section to maintain the position of the parts during pouring of the slabs.

11. A flexible dowel for use with a filler strip of an expansion joint including elements to be bonded in adjacent slabs of the joint during pouring of the slabs, said elements being con- 1 structed and arranged to take tension and compression to provide effective load transference from one slab to the other adjacent the joint, said elements being flexibly connected by a section unitary therewith to permit relative movement of the elements during expansion and contraction of the slabs without interfering with the load transferring function of the elements.

12. A construction as described in claim 11, including plates to be secured to the filler strip and supporting and positioning the elements.

13. A construction as defined in claim 11, wherein the elements have upper portions embedded in one slab on one side of the joint and lower portions embedded'in the other slab on the opposite side of the joint.

14. A flexible dowel for expansion joints, comprising elements to be embedded in adjacent parts defining the joint, and a relatively rigid element to take tension and compression integral with the first mentioned elements for permitting relative movement thereof during'expansion and contraction of the joint.

15. A flexible dowel for expansion joints, comprising a normally vertical truss section for disposition between the parts defining the joint, said truss section being constructed and arranged to take tension and compression and horizontal sections extending in opposite directions from the upper and lower ends of the truss section for rigid bonding with the parts defining the joint, the junctions between the truss section and the horizontal sections being flexible for permitting relative movement of the horizontal sections during expansion and contraction of the joint.

16. An expansion joint for adjacent concrete slabs of a road bed including a filler strip between the slabs and having an opening therein, a plate secured to the filler strip at each side of the opening therein, each plate having an opening adjacent the upper and lower ends thereof and on opposite sides of the vertical center line of the plate, a pair of bars each having vertically spaced horizontal sections embedded'in the adjacent slabs, and a vertical section disposed between the plates, the horizontal sections of each bar extending through the upper opening of one plate and the lower opening of the other plate.

17. A construction as defined in claim 16, wherein each plate is provided with elongated depressions in vertical alinement with the openings therein to permit angular movement of the vertical sections of the bars under extreme expansion of the slabs.

18. A construction as defined in claim 16, wherein each plate is provided with a projection adjacent to and vertically alined with each opening therein for centering engagement by the vertical sections of the bars.

19. A construction as defined in claim 16, wherein the upper horizontal sections of the bars at their opposed ends are provided with vertically disposed supporting sections.

20. A flexible dowel for expansion joints, comprising spaced parallel sections for rigid connection with adjacent parts defining the joint, and a section constructed and arranged to take tension and compression unitary with and fiexifor permitting relative movement thereof during expansion and contraction of the joint.

21. In an expansion joint for concrete road work, a bar having vertically spaced horizontal portions bonded in adjacent concrete slabs, a normally vertical portion extending between the slabs and flexibly interconnecting the horizontal portions, and a vertical supporting portion 'connected with one of said horizontal portions with the lower end thereof terminating adjacent the road bed surface.

22. An expansion joint for adjacent ends of concrete slabs comprising a bar having vertically spaced horizontal portions bonded in the slabs, a substantially rigid vertical portion to take tension and compression extending between the slabs and flexibly interconnecting the horizontal portions, centering projections internally of the connections between the horizontal and vertical portions, and expansion depressions externally of said connections.

ELMER J. WEBB. 

